Plif opposing wedge ramp

ABSTRACT

A spinal fusion implant for implantation between adjacent vertebrae is formed in the approximate shape of a hollow cube. The device has an upper section and a lower section separated by a distractor all of which are relatively movable. The sidewalls of the upper section and the lower section terminate in inclined planes so that the sections move away from each other as the wedge shaped distractor increases the height of the device.

RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 10/776,663 filed Feb. 10, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of orthopedic surgery and, moreparticularly, to implants to be placed between vertebrae in the spine.

2. Background of the Invention

Spinal stabilization is one approach to alleviating chronic back paincaused by displaced disk material or excessive movement of individualvertebrae. Conventional stabilization techniques include fusing two ormore vertebrae together to circumvent or immobilize the area ofexcessive movement. Normally, the vertebral disk material whichseparates the vertebrae is removed and bone graft material is insertedin the space for interbody fusion. In addition to or, in place of, thebone graft material, a spinal implant may be inserted in theintervertebral space.

The conventional surgical approach for stabilization has beenposteriorly for ease of access to the spine and to avoid interferingwith internal organs and tissue. Usually the implant site is prepared tomaintain natural lordosis and to accept a certain sized implant withincertain pressure limits. This requires considerable time and skill bythe surgeon.

DESCRIPTION OF THE PRIOR ART

U.S. Pat. No. 6,562,074 to Gerber et al issued May 13, 2003 discloses aspinal insert which can be manipulated to adjust the height of theimplant through links connected to the upper and lower plates.

U.S. Pat. No. 6,120,506 issued Sep. 19, 2000 to Kohrs et al discloses alordotic implant and a tap for use in preparing the vertebrae. Theimplant is designed to be inserted between the non-parallel end platesof adjacent vertebrae and maintain the natural lordotic angle of thespine. This is done through the use of a threaded tapered plug insertedin a tapped hole in the direction required by the lordosis of the spine.The implant is hollow and has radial apertures for accommodating bonegraft material.

U.S. Pat. No. 6,015,436 issued Jan. 18, 2000 to Shoenhoeffer discloses atubular spinal implant. The implant is hollow and has radial aperturesfor interbody fusion through bone growth material. The device is placedbetween adjacent vertebrae with the opposite ends of the tube contactingthe opposing vertebrae. The opposite ends are threaded together to formthe hollow tube.

SUMMARY OF THE INVENTION

The implant of this invention has a main body having upper and a lowersections with mating sidewalls relatively movable along an inclinedramp. The inclined ramp forms a wedge movable between inclined sidewallsof the main body sections. The main body sections and the inclined rampform a hollow cube-shaped structure with common open sides. The implantis inserted in an extended thin mode between adjacent vertebrae and theramp is inserted between the sections through one end. The body sectionsare connected at the other end by a link which permits the sections tomove vertically away from each other for increasing the height of theimplant and engaging the opposing surfaces of adjacent vertebrae. Theadjacent vertebrae are forced apart as the height of the implantincreases. The spinal fusion device may be used unilaterally orbilaterally.

Accordingly, it is an objective of the instant invention to teach aposterior surgical approach for placement of an adjustable spinalimplant for interbody fusion allowing the implant to be inserted througha small incision and increased in size in situ.

It is another objective of the instant invention to teach a spinalimplant which allows the surgeon to provide for lordosisintraoperatively and to distract through the implant.

It is a further objective of the instant invention to teach a spinalimplant having increased contact area in the disk space.

It is yet another objective of the instant invention to teach an implantfacilitating interbody fusion through bone graft or an ingrowth-typeimplant.

Other objectives and advantages of this invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The drawings constitutea part of this specification and include exemplary embodiments of thepresent invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of the spinal fusion implant of this inventionin the thin mode;

FIG. 2 is a perspective of the spinal fusion device of this invention inthe deployed mode;

FIG. 3 is a side view, partially in section, of the implant of FIG. 2;

FIG. 4 is an end view in perspective another embodiment of the implantof this invention in the thin mode;

FIG. 5 is a perspective of the spinal fusion device of FIG. 4 of thisinvention in the deployed mode; and

FIG. 6 is a side view, partially in section, of the implant of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The spinal fusion device 10 is inserted in the intervertebral space inthe insertion mode, shown in FIG. 1, to replace damaged, missing orexcised disk material. This extended position allows the leading end ofthe implant to be inserted in a small intervertebral space without thenecessity of excising structurally sound bone. The upper section 11 hasa top surface 12 for engaging the end plate of a vertebra and the lowersection 13 has a bottom surface 14 for engaging the end plate of anadjacent vertebra. The top surface 12 and the bottom surface 14 areplanar to provide a large contact area with each vertebra. Each contactsurface has a roughened finish to provide better purchase on the endplates of the vertebrae. As shown, the top and bottom surfaces have aseries of lands and grooves 15, 16, 17 and 18 though other stippledtreatment may be employed. Of course, the device may be rotated aboutits longitudinal axis 180 degrees so that the upper section becomes thelower section and vice versa.

The device 10 has two extreme positions and is adjustable infinitelybetween those positions, eg., in the insertion mode, the extendedposition of the leading end of the structure has a height 20approximately the same as the height of the sections and a lengthapproximately twice the length of one section, as shown in FIG. 1. Inthe increased height mode, the expanded position, shown in FIG. 2, theheight 19 is the sum of the height of the individual sections with thedistractor 42 and the length is approximately the same as the length ofa section.

The fusion device 10 may be made of conventional materials used forsurgical implants, such as stainless steel and its many differentalloys, titanium, and any other metal with the requisite strength andbiologically inert properties. Polymeric materials with adequatestrength and biological properties may also be used in the constructionof the fusion device.

The upper section 11 is formed with an end wall 21 a top surface 12 anddepending sidewalls 22 and 23. The sidewalls terminate in an inclinedplane 24 which extends from the end wall 21 to the top surface 12. Thetop surface 12 has a large aperture 25 therethrough to provide for boneingrowth. The top surface 12 has a narrower groove 26 extending alongthe sidewalls 22 and 23. The groove 26 engages the flange 43 ofdistractor 42 to guide the relative movement of the sections maintainingthe distractor 42 and the depending sidewalls in alignment. The link 40has a bore 27 with internal threads 28 to cooperate with the threads 41on the link 40.

The bottom surface 14 of the lower section 13 has a large aperture 30,as shown in FIG. 1, to facilitate bone ingrowth after implantation. Thelower section 13 is a U-shaped channel with opposed upstanding sidewalls31 and 32 projecting from the bottom surface. The side walls 31 and 32have a short end 33 and a long end 34. The sidewalls 31 and 32 terminatein an inclined plane extending from the short end 33 toward the long end34. The upstanding walls each have a groove 35 along the edge of theinclined plane. The movement of the flange 44 through the groove 35contributes to the alignment of the distractor 42 and lower section asthey move relative to each other.

The ends of the inclined planes of the upstanding and depending wallsare smooth ramps to provide ease in the relative sliding contact betweenthe distractor and upper and lower section surfaces. Other embodimentsof the complementary surfaces may provide additional or substituteguidance to maintain the upper and lower sections in alignment duringmovement of the contacting surfaces of the inclined planes, such as, theends of the inclined planes may be sloped across the thickness of theside walls or a stepped ramp may be used.

The ramp or distractor 42 is dimensioned to be inserted into thetrailing end of the interior cavity between the upper section and thelower section of the spinal infusion device 10, as shown in FIG. 1. Anend wall 36 is dimensioned to close the opening formed in the trailingend between the upper section 11 and the lower section 13 by thedepending and upstanding sidewalls. The upper surface of the plug has aninclined ramp on each side to accommodate the inclined plane 24 of thedepending walls 22 and 23 of the upper section. The end wall 36 has alarger circumferential end dimensioned to extend to the outer peripheryof the upper and lower sections to make a smooth trailing end outersurface. Extending from the end wall 36 into the cavity of the hollowstructure 10 is the body 47 of the distractor 42. The body is connectedto the end wall 36 by two rails 48 and 49 leaving the central area openfor bone ingrowth. The end plug 36 has a bore 61 aligned with bore 60 inlink 40. The bore 61 has a larger countersunk bore 63 in the end wall36. These bores are aligned with the threaded tube 29 attached to thelink 40, as shown in FIG. 3.

The leading ends of the upper and lower sections are formed with avertical slot 64. Link 40 includes an upper flange 65 and a lower flange66 of a size and shape to slide within the vertical slot 64 as thedistractor 42 moves into the central cavity foreshortening the implantand increasing the distance between the leading ends of the sections.The threaded tube 29 surrounds the bore 60 and extends toward the bore61. A jack screw 67 is inserted through bore 61 engaging the threads inthe tube 27. As the jack screw 67 is tightened, the ramp is drawn towardthe leading end of the implant and the leading ends of the upper andlower sections slide apart along flanges 65 and 66.

The spinal fusion device is inserted in the disk space between adjacentvertebrae in the extended position with the top surface in contact withthe end plate of one vertebra and the bottom surface in contact with theend plate of an adjacent vertebra. The surgeon turns the jack screw 67causing the upper and lower sections to move along the complementaryinclined plane to shorten the fusion device and increase the distancebetween the end plates of the adjacent vertebrae. The adjustment maycontinue until the optimum distance between vertebrae has been reached.At this time, the jack screw may be removed and replaced by a bolt (notshown) of sufficient length to retain the upper and lower sectionstogether.

In FIGS. 4, 5 and 6, another embodiment of the implant 10 is illustratedwith integral brackets on the upper and lower sections for engagingadjacent vertebrae. Each bracket has apertures therethrough for placingbone screws into the adjacent vertebra. The bone screws add stability tothe implant and provide additional security to prevent dislodgement ofth implant under normal activity.

The upper section has a bracket 70 attached to the trailing end wall. Asshown, the bracket extends normal to the top surface 12 in a directionaway from the distractor 42. The lower section 13 has a bracket 71attached to the trailing end wall and extending in the oppositedirection from the lower section. Each bracket 70, 71 is shown withcountersunk apertures 72, 73, 74 and 75. Bone screws 76, 77, 78 and 79are inserted into the apertures and threaded into the vertebrae.

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiment but only by the scope ofthe appended claims.

1. A spinal fusion device for adjusting the space between vertebraecomprising an upper section having a first end, a top surface anddepending sidewalls, said sidewalls terminating in a first inclinedplane, a lower section having a second end, a bottom surface andupstanding sidewalls, said upstanding sidewalls terminating in a secondinclined plane, said upper section and said lower section movablyconnected in a first thin relationship and means connected to said uppersection and said lower section for moving said first section and saidsecond section into a second thicker relationship.
 2. A spinal fusiondevice for adjusting the space between vertebrae comprising an uppersection having a top surface and depending sidewalls, said dependingsidewalls terminating in a first inclined plane, a lower section havinga bottom surface and upstanding sidewalls, said upstanding sidewallsterminating in a second inclined plane, and a distractor located betweensaid upstanding sidewalls and said depending sidewalls, said distractorhaving adjustment means for moving said distractor relative to saidupper section and said lower section thereby increasing the distancebetween said top surface and said bottom surface.
 3. A spinal fusiondevice for placement in the disk space between adjacent vertebraecomprising a hollow body having an upper section with a top surface forcontacting one vertebra and a lower section with a bottom surface forcontacting the adjacent vertebra, said top surface and said bottomsurface having means for engaging adjacent vertebrae, dependingsidewalls extending from said top surface terminating in a firstinclined plane, upstanding sidewalls projecting from said bottom surfaceterminating in a second inclined plane, said upper section having afirst end wall, said lower section having a second end wall, a linkslidably mounted in said first end wall and said second end wall wherebysaid upper section and said lower section may move apart.
 4. A spinalfusion device of claim 3 wherein a distractor is slidably disposedbetween said depending sidewalls and said upstanding sidewalls, saiddepending sidewalls and said upstanding sidewalls in sliding contactwith said distractor along said first inclined plane and said secondinclined plane whereby the distance between said bottom surface and saidtop surface is adjustable by moving said upper section relative to saidlower section.
 5. A spinal fusion device of claim 4 wherein said linkincludes a tube with internal threads, said distractor includes a bore,a jack screw in said bore threaded into said tube whereby saiddistractor moves relative to said upper section and said lower sectionas said jack screw is threaded into said tube.
 6. A spinal fusion deviceof claim 4 wherein said upstanding walls have a second groove along saidsecond inclined plane, a second flange connected to said distractor,said second flange adapted to contact said portion of said second grooveand provide alignment of said upper section and said lower section.
 7. Aspinal fusion device of claim 6 wherein said depending walls have agroove along said first inclined plane, a flange connected to saiddistractor, said flange adapted to contact said portion of said grooveand provide alignment of said upper section and said lower section.
 8. Aspinal fusion device of claim 4 wherein said depending walls have agroove along said first inclined plane, a flange connected to saiddistractor, said flange adapted to contact said portion of said grooveand provide alignment of said upper section and said lower section.
 9. Aspinal fusion device of claim 3 wherein said means for engaging avertebra is a series of lands and grooves on said top surface.
 10. Aspinal fusion device of claim 9 wherein said means for engaging avertebra is a series of lands and grooves on said bottom surface.
 11. Aspinal fusion device of claim 10 wherein said means for engaging avertebra is a bracket on said bottom surface.
 12. A spinal fusion deviceof claim 11 wherein said means for engaging a vertebra is a bracket onsaid top surface.
 13. A spinal fusion device of claim 3 wherein saidmeans for engaging a vertebra is a bracket on said top surface.
 14. Aspinal fusion device of claim 3 wherein said means for engaging avertebra is a bracket on said bottom surface.